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Concretionary methane-seep carbonates and associated microbial communities in Black Sea sediments [An article from: Palaeogeography, Palaeoclimatology, Palaeoecology] | Digital

by J. Reitner (Author), J. Peckmann (Author), M. Blumenberg (Author), Michaelis (Author)

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Elsevier

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This digital document is a journal article from Palaeogeography, Palaeoclimatology, Palaeoecology, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: Gas seeps in the euxinic northwestern Black Sea provide an excellent opportunity to study anaerobic, methane-based ecosystems with minimum interference from oxygen-dependent processes. An integrated approach using fluorescence- and electron microscopy, fluorescence in situ hybridization, lipid biomarkers, stable isotopes (@d^1^3C), and petrography revealed insight into the anatomy of concretionary methane-derived carbonates currently forming within the sediment around seeps. Some of the carbonate concretions have been found to be surrounded by microbial mats. The mats harbour colonies of sulphate-reducing bacteria (DSS-group), and archaea (ANME-1), putative players in the anaerobic oxidation of methane. Isotopically-depleted lipid biomarkers indicate an uptake of methane carbon into the biomass of the mat biota. Microbial metabolism sustains the precipitation of concretionary carbonates, significantly depleted in ^1^3C. The concretions consist of rectangularly orientated, rod- to dumbbell-shaped crystal aggregates made of fibrous high Mg-calcite. The sulphate-reducing bacteria exhibit intracellular storage inclusions, and magnetosomes with greigite (Fe"3S"4), indicating that iron cycling is involved in the metabolism of the microbial population. Transfer of Fe^3^+ into the cells is apparently mediated by abundant extracellular vesicles resembling known bacterial siderophore vesicles (marinobactine) in size (20 to 100 nm) and structure. nd structure.